How many seconds are required for observing lack of smooth pursuit during the HGN test?

During the Horizontal Gaze Nystagmus (HGN) test, the observer must look for the lack of smooth pursuit, which is one of the indicators of potential impairment. To accurately assess this, an observation period of 2 seconds for each eye is standard. This timeframe allows the officer to adequately note any jerking movements of the eye as it moves horizontally. If the eye does not move smoothly along the desired path, it suggests a possible impairment due to alcohol or other substances. A longer duration might lead to unnecessary delays or increase the risk of external factors influencing the observation, while a shorter duration may not provide enough time to make a reliable assessment. Thus, the 2-second observation is crucial for ensuring the accuracy of the test results.